Self-venting balloon dilatation catheter and method

ABSTRACT

Self-venting balloon dilatation catheter having a flexible tubular member with first and second lumens extending therethrough. An inflatable balloon is carried by the distal extremity of the tubular member in such a manner so that the first lumen extends through the balloon and is out of communication with the interior of the balloon and the second lumen is in communication with the interior of the balloon. A venting device is disposed between the balloon and the tubular member for venting air from the interior of the balloon but inhibiting the escape of liquid from the balloon.

This is a division of application Ser. No. 760,637, filed July 30, 1985,now U.S. Pat. No. 4,638,805.

This invention relates to balloon dilatation catheters and moreparticularly to such catheters having a self-venting balloon and amethod for making the same.

In utilizing balloon dilatation catheters, it is necessary that theballoon be filled with a liquid. In the filling of the balloon, it isdesirable that the air which is within the balloon be expelled from theballoon but the air is compressible. In the past this has beenaccomplished by successively aspirating the balloon with fluid. The airis withdrawn during the repeated evacuation. This has a disadvantage inthat it can be difficult to ensure complete removal of all the air.Alternatively, the air removal is accomplished by providing a separatetube which may be removable which extends from the proximal extremity ofthe catheter into the balloon so that during the time that the liquid isbeing introduced into the ballon, the air in the balloon can be expelledthrough the separate tube. The use of such a separate tube has adisadvantage, particularly when it is desired to provide a dilatationcatheter which has a very low profile in that it makes it more difficultto reduce the profile of the dilatation catheter. There is therefore aneed for a new and improved balloon dilatation catheter which overcomesthese limitations.

In general, it is an object of the present invention to provide aballoon dilatation catheter which is self-venting.

Another object of the invention is to provide a dilatation catheter ofthe above character in which the air is vented through the distalextremity of the catheter.

Another object of the invention is to provide a balloon dilatationcatheter of the above character in which the air in the balloon isvented while the leakage of any liquid from the balloon is inhibited.

Another object of the invention is to provide a balloon dilatationcatheter of the above character which ensures complete removal of theair without aspiration.

Another object of the invention is to provide a method for constructingthe catheter of the present invention.

Additional objects and features of the invention will appear from thefollowing description in which the preferred embodiment is set forth indetail in conjunction with the accompanying drawing.

FIG. 1 is a side elevational view of a balloon dilatation catheterincorporating the present invention.

FIG. 2 is a cross sectional view of the distal extremity of the balloondilatation catheter shown in FIG. 1.

FIG. 3 is a cross sectional view taken along the line 3--3 of FIG. 2.

FIG. 4 is a cross sectional view showing the method which is utilized inmanufacturing the balloon dilatation catheter shown in FIGS. 1-3.

In general, the self-venting balloon dilatation catheter of the presentinvention is comprised of a flexible tubular member having first andsecond lumens extending therethrough. An inflatable balloon is carriedby the distal extremity of the tubular member in such a manner so thatthe first lumen extends through the balloon and is out of communicationwith the interior of the balloon and the second lumen is incommunication with the interior of the balloon. A vent system isdisposed between the balloon and the tubular member for venting air fromthe interior of the balloon but inhibiting the escape of liquid from theballoon.

More in particular as shown in FIGS. 1-3 of the drawing, the balloondilatation catheter 10 incorporating the present invention is comprisedof a tubular member 11 which consists of a first tubular element 12which has a lumen 13 extending therethrough. It also consists of asecond tubular element 14 which is coaxially disposed on the firsttubular element 12 and provides in conjunction with the first tubularelement an annular lumen which extends longitudinally of the first andsecond tubular elements 12 and 14. An expandable balloon 17 is carriedby the second tubular element 14 of the member 11 near the distalportion thereof and has its interior in communication with the lumen 16.The balloon 17 extends concentrically about the first tubular element12. Although the balloon 17 can be formed as a separate element whichhas its extremities bonded to the second tubular element 14, it ispreferably formed integral with the second tubular element as shown. Thetubular elements 12 and 14 are formed of a suitable flexiblethermo-plastic material such as a polyolefin or polyvinylchloride.

The distal extremities of the first and second tubular elements 12 and14 are bonded together in a suitable manner so as to form a liquid-tightseal between the same. Typically this can be accomplished by applyingheat to the distal extremity of the second tubular element with amandrel disposed in the distal extremity of the first tubular elementand applying heat to shrink the distal extremity of the second tubularelement onto the first tubular element to form such a seal.

Means is provided in the distal extremity of the first and secondtubular elements for venting air from the balloon 17 while inhibitingthe escape of liquid from the balloon 17 and consists of a very smallpassage 21 which is disposed between the distal extremities of the firstand second tubular elements 12 and 14 and which extends from theinterior of the balloon 17 to ambient at the distal extremity of thecatheter 11. The flow passage 21 can be formed in any suitable manner.One method found to be particularly efficacious is as follows inconjunction with FIG. 4. A piece 22 of suitable wire such as tungsten isused because of its good tensile strength. The wire 22 should have adiameter which is less than 0.001 inches as, for example, 0.0005 inches.It is coated with silicone. After the wire 22 has been coated withsilicone, it is inserted by a tweezers between the distal extremities ofthe first and second tubular elements 12 and 14 prior to the time thatthe second tubular element 14 is heat shrunk onto the first tubularelement as hereinbefore described. As soon as the tungsten wire 22 hasbeen inserted into the distal extremities of the first and secondtubular elements 12 and 14 so that it extends into the balloon 17 andout the distal extremities as shown in FIG. 4, a mandrel 23 is insertedinto the lumen 13. Heat is then applied to the distal extremity of thesecond tubular element 14 to cause it to form a shrink fit between itand the distal extremity of the first tubular element 12 and at the sametime to shrink down around the wire 22. After the distal extremity ofthe catheter has been cooled, the mandrel 23 can be removed and the wire22 can be pulled out with tweezers leaving the cylindrical flow passage21 hereinbefore described.

It should be appreciated that if desired, more than one hole or passage21 can be provided to make the balloon venting procedure more rapid. Italso should be appreciated that other means can be provided in thedistal extremity of the catheter in place of the passage 21 for makingthe balloon 17 self-venting. For example, braided fibers can be utilizedin the distal extremity of the catheter in the same manner as thetungsten wire 22 has been utilized. In such a case, the fibers can beleft in place so that the air can flow between interstices of thebraided fibers. Alternatively, hollow fiber or fibers can beincorporated into the distal extremity of the catheter. Alternatively,hydrophobic filter material can be incorporated between the distalextremities of the first and second tubular elements 12 and 14. Thisfilter material is capable of passing air but inhibits the passage ofliquid from the balloon 17.

The remainder of the balloon dilatation catheter shown in FIG. 1 issubstantially conventional. A side arm adapter 26 is provided which hasa main or central arm 27 and a side arm 28. A guide wire 29 extendsthrough the main or central arm 27 and extends through the lumen 13 ofthe first tubular element 12 and has a distal extremity extending beyondthe distal extremity of the dilatation catheter 11. A torquer 31 issecured to the proximal extremity of the guide wire 29 and is utilizedfor extending and retracting the guide wire and also for rotating theguide wire.

Use of the self-venting balloon dilatation catheter may now be brieflydescribed as follows. The balloon 17 is first inflated outside of thehuman body by introducing a radiographic contrast liquid through theside arm 28 so that is passes through the annular lumen 16 between thefirst and second tubular elements 12 and 14 and passes into the balloon17. The air which is in the balloon is pushed forwardly in the balloonand under the pressure of the radiographic contrast liquid is forced topass out through the small passage 21 provided between the distalextremities of the first and second tubular elements 12 and 14. Byutilizing a passage 21 having a diameter of 0.0005 inches, it has beenfound that a two millimeter diameter balloon having a length ofapproximately 25 millimeters can be completely rid of air in less thanapproximately 40 seconds. The size of the passage 21 is such that itinhibits the escape of the radiographic contrast liquid so that verylittle, if any, of the liquid can escape, even though pressures up to200 psi for the radiographic contrast liquid is attained within theballoon 17. As soon as the balloon 17 has been inflated with theradiographic contrast liquid and the air has been expelled therefromthrough the passage 21, the liquid can be withdrawn to deflate theballoon 17. The balloon dilatation catheter is now ready to be insertedinto the human body. After the balloon 17 has been positioned in thestenosis in the arterial vessel in the human body, the balloon can beagain inflated by reintroducing radiographic contrast liquid through theside arm 28 through the lumen 16 and into the balloon 17. Since all ofthe air has previously been expelled from the balloon 17, the ballooncan be readily inflated within the stenosis to its full diameter at thedesired pressure as, for example, in excess of 100 psi without danger ofany significant amount of radiopaque contrast liquid passing through thepassage 21. After the opening in the stenosis has been enlarged, theballoon can be deflated and the dilatation catheter can be removed.

It is apparent from the foregoing that there has been provided a balloondilatation catheter which is self-venting and in which the balloon canbe inflated to the desired pressure without danger of any significantamount of radiopaque contrast liquid passing through the venting orificeprovided in the distal extremity of the balloon dilatation catheter. Theventing orifice formed in the distal extemity of the balloon dilatationcatheter is formed in such a manner so that it can be readilyincorporated into the manufacturing process for making the balloondilatation catheters.

What is claimed is:
 1. In a method for fabricating a self-ventingballoon dilatation catheter, providing a first tubular element having alumen extending therethrough, providing a second tubular element havinga lumen disposed therein, forming a balloon onto the second tubularelement near the distal extremity of the second tubular element, placingthe first tubular element within the second tubular element so that thesecond tubular element extends coaxially of the first tubular elementand forming a flow passage open to ambient between the distalextremities of the first and second tubular elements and incommunication with the interior of the balloon which has a size lessthan 0.001 inches to permit the escape of air from the interior of theballoon but inhibiting the escape of liquid from the interior of theballoon.
 2. In a method for fabricating a self-venting balloondilatation catheter, providing a first tubular element having a lumenextending therethrough, providing a second tubular element having alumen disposed therein, forming a balloon onto the second tubularelement near the distal extremity of the second tubular element, placingthe first tubular element within the second tubular element so that thesecond tubular element extends coaxially of the first tubular element,forming a flow passage between the distal extremities of the first andsecond tubular elements and in communication with the interior of theballoon which has a size less than 0.001 inches to permit the escape ofair from the interior of the balloon but inhibiting the escape of liquidfrom the interior of the balloon, said flow passage being formed byintroducing a wire between the distal extremities of the first andsecond tubular elements, forming the second tubular element of a heatshrinkable plastic, placing a mandrel in the lumen of the first tubularelement in the distal extremity of the first tubular element, applyingheat to the distal extremity of the second tubular element to heatshrink it onto the first tubular element, permitting the distalextremities of the first and second tubular elements to cool, removingthe mandrel from the lumen of the first tubular element and removing thewire from between the first and second tubular elements to provide theflow passage.
 3. A method as in claim 2 wherein said wire is formed oftungsten to facilitate the transfer of heat and to facilitate removal ofthe wire.